In many optical communication systems, the data-modulated optical carrier undergoes amplification between the optical transmitter and the optical receiver. One type of optical amplification involves conversion of a data-modulated optical carrier from an optical signal to an electrical signal and a re-conversion of a corresponding electrical back to an optical signal. Such a conversion and re-conversion sequence is typically referred to as optical to electrical to optical (OEO) type of signal processing. Another type of optical amplification involves amplification of the data-modulated optical carrier in the optical domain without any type of OEO signal procession. This later type of optical amplification is often referred to as all-optical amplification. All-optical amplification has been performed using laser pumping of a fiber doped with rare-earth dopant atoms.
In long-distance optical communication systems, OEO and/or all-optical amplification is often needed to compensate for attenuation of the data-modulated optical carrier in passive optical transmission fibers.